/Engine/Source/Runtime/InteractiveToolsFramework/Public/BaseGizmos/GizmoRenderingUtil.h
This is a local estimate and is increasingly incorrect as the 3D point gets further from Location
Conversion factor between pixel and world-space coordinates at 3D point Location in View.
namespace GizmoRenderingUtil { float GizmoRenderingUtil::CalculateLocalPixelToWorldScale ( const [FSceneView](API\Runtime\Engine\FSceneView) * View, const FVector & Location ) }